Askarels, which are mixtures of polychlorinated biphenyls (PCB's ) and chlorobenzenes, were commonly used as dielectric liquid coolants in electrical induction apparatus such as transformers for many years until it was realized that the PCB's represented an environmental and physiological hazard. Since the replacement of these PCB containing transformers as well as the disposal of the contaminated transformers together with the PCB's is an expensive undertaking, various processes have been proposed to preserve and decontaminate the transformers by replacing the PCB's with a safe dielectric liquid coolant. The dielectric liquid coolants of choice are the silicone oils, particularly trimethylsilyl end-blocked poly-dimethylsiloxanes), which have the following formula: ##STR1## wherein n is of a value sufficient to provide an acceptable viscosity, e.g., a viscosity at 25.degree. C. of about 50 centistokes or less. One process for the replacement of askarels with silicone oil is described in United States patent application Ser. No. 739,775, filed on June 3, 1985, now U.S. Pat. No. 4,744,905, issued on May 17, 1988, which is incorporated by reference herein. It will be seen from this patent application that the askarels become trapped in the cellulose interstices of the transformers and that chlorobenzenes or other interim dielectric fluids and silicone oil are used to leach out the PCB's over time. Thus, mixtures of silicone oil, chlorobenzenes, and PCB's are continuously removed from the transformer in order to reduce the PCB elution rate to an acceptable number. A typical mixture, as removed from the transformer, contains about 4 to 13 percent by weight chlorobenzenes, about 0.05 to about 0.15 percent by weight PCB's (500 to 1500 ppm), and the balance silicone oil. The percentages by weight are based on the total weight of the mixture. The silicone oil and the chlorobenzenes, of course, represent valuable commodities provided, however, that the PCB's are removed.
It has been suggested to pass the mixture of silicone oil, chlorobenzenes, and PCB's through a bed or a series of beds of activated carbon, which would adsorb the PCB's. The activated carbon is not selective for the PCB's, however, and also adsorbs the chlorobenzenes. Unfortunately, such a large quantity of activated carbon is required to adsorb both the chlorobenzenes and the PCB's that the process becomes uneconomical. If the activated carbon adsorption is accomplished by passing the mixture through drums of activated carbon, the economies become even poorer because of the need for excessive drum handling. In addition, once the chlorobenzenes and the PCB's are adsorbed onto the activated carbon, the chlorobenzenes cannot be recovered, at least in a way that is commercially feasible.